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Muddy Waters

Earthquakes happen often. But it’s not after every earthquake that you find a new island in your backyard. That, however, was just what the city of Gwadar, Pakistan woke up to on the morning of September 24 after a magnitude 7.7 earthquake shook the region. The island, located roughly 100 meters (350 feet) offshore, is 6 to 12 m (20 to 40 feet) high and 30 m (100 ft) wide. Although geologists are still undecided about how it formed, the leading hypothesis is that the island is a mud volcano.

So what is a mud volcano and why does this phrase make me giggle every time I say it? Mud volcanoes form when trapped sediments liquefy and begin to flow under pressure. This is often the reason why building foundations destabilize and shift during earthquakes. In the case of Pakistan, this pressure buildup is caused by hot gas trapped as one tectonic plate is pushed (subducted) beneath another. The September 24 earthquake allowed some of this gas to escape, pushing mud and water to the surface. And although this sounds like something you would’ve loved to make in your sandbox as a child, the eruption of hot pressurized sediments is probably not as cute as it might seem.

The unstable island will likely not be around for long before erosion and settling cause it to disappear below the ocean surface. However, this hasn’t stopped inquisitive locals from doing some snooping around. Visitors to the island have reported hearing the hissing of escaping gas and seeing dead fish floating in the surrounding water. Tests have established that the escaping gases are flammable, but this hasn’t stopped some visitors from enjoying a casual smoke. Moral of the story? Next time a mysterious island appears in your backyard, don’t smoke. Call a geologist.